1. Field of the Invention
The present invention relates to magnetic disk drives, and more particularly, to generating repeatable runout (RRO) cancellation information during self servowriting of tracks on a rotating magnetic disk medium of a disk drive.
2. Description of the Prior Art and Related Information
With reference to FIGS. 7A and 7B, repeatable runout (RRO) in a disk drive results from imperfections, with respect to a perfect circle, in the location of servo information 34 along a track 26 on a disk surface in the disk drive. During track following, the RRO imperfections have a detrimental effect on efforts by a head-position servo control loop to cause a transducer head to follow a perfect circle. The RRO imperfections are relatively static over time and the effect of the RRO may be attenuated by measuring the RRO and storing resulting RRO cancellation values for later use by the head-position servo loop to compensate for the RRO. However, measuring the RRO may be time consuming and may affect the manufacturing cost the disk drive.
Accordingly, there exists a need for a technique for efficiently determining the RRO cancellation information for reducing the effects of RRO in a disk drive. The present invention satisfies these needs.